1. Field of the Invention
This invention relates to an antenna apparatus and a portable wireless communication apparatus.
2. Description of the Prior Art
An antenna apparatus including a microstrip antenna is known and a portable wireless communication apparatus including the antenna apparatus including a microstrip antenna is also known.
In a portable wireless communication apparatus (a mobile or base station) of a semi-microwave band, a microstrip antenna or a monopole antenna is used. The microstrip antenna includes a square or a circular planer element above a ground plane at a constant interval. The length of the planer element is generally a half wavelength (referred to as a half wavelength microstrip antenna). This half wavelength microstrip line antenna has directivity in the direction perpendicular to the plane of the microstrip line. The main polarizing direction is single and corresponds to the edge of the microstrip line of which length is a half wavelength.
The monopole antenna apparatus includes a monopole antenna (linear element) arranged perpendicularly to an edge of the ground plane. This monopole antenna is fed in an unbalanced condition with respect to the ground plane. The length of the monopole antenna is generally a half wavelength or a quarter wavelength. The main polarizing direction is single and corresponds to an axial direction of the monopole antenna.
FIG. 17 is a perspective view of a monopole antenna of a prior art. This monopole antenna apparatus includes a monopole antenna 1 connected to a matching circuit 19 on a ground plane 6. The feed point impedance of the monopole antenna 1 is made 50 xcexa9 by the matching circuit 19.
FIG. 18 is a graphical drawing showing prior art directivity of the monopole antenna shown in FIG. 17 on the XZ plane. The solid line represents the vertical polarizing component 20 and the chain line represents the horizontal polarizing component 21.
As shown in FIG. 18, the average level of the vertical polarizing component 20 is extremely higher that of the horizontal polarizing component 21 and has a directivity of letter xe2x80x9c8xe2x80x9d. As mentioned above, the microstrip antenna apparatus has the single main polarizing direction same as the monopole antenna apparatus has.
Another prior art antenna apparatus included in a portable wireless communication apparatus is disclosed in Japanese patent application provisional publication No. 57-103406. In this document, adjusting the offset distance of the feed point provides the desired input impedance.
FIG. 19 is such a prior antenna apparatus of which feed point is offset to provide the desired input impedance. This antenna apparatus is called a planer inverted-F antenna. In the planer inverted-F antenna, the corner of the plate conductor of the inverted-F antenna 2 is connected to the ground plane 6 and the feed portion 4 is connected a point of the plate conductor which is offset from the grounding point to obtain the desired input impedance. When the planer inverted-F antenna is viewed from the external on the plane of the ground plane, there is an outline of the letter xe2x80x9cFxe2x80x9d. Thus, this type of the antenna apparatus is called (planer) inverted-F antenna.
FIG. 20 is a graphical drawing showing the directivity of the prior art planer inverted-F antenna. In FIG. 20, the solid line represents the vertical polarizing component 22 and the chain line represents the horizontal polarizing component 23. In this planer inverted-F antenna apparatus, the level of the horizontal polarizing component 23 is slightly higher than that of the vertical polarizing component 22.
Estimating the characteristic of the antenna apparatus uses a pattern averaged gain (PAG) on the horizontal plane when a human being carries the portable wireless communication apparatus.
The PAG is given by equation (1) in the condition that the head of the human being holding the portable wireless communication including the antenna apparatus is positioned at the origin of the XYZ axes in Z direction .                     PAG        =                              1                          2              ⁢              π                                ⁢                                    ∫                              2                ⁢                π                            1                        ⁢                                          [                                                                            G                      θ                                        ⁡                                          (                      φ                      )                                                        +                                                                                    G                        φ                                            ⁡                                              (                        φ                        )                                                              XPR                                                  ]                            ⁢                              xe2x80x83                            ⁢                              ⅆ                φ                                                                        (        1        )            
In Eq. (1), G xcex8 (xcfx86) and G xcfx86 (xcfx86) represent power directivities of the vertical polarizing component and the horizontal polarizing component on the horizontal plane (XY plane), respectively. XPR represents a crossing polarizing power ratio, that is, a power ratio of the vertical polarizing components to the horizontal polarizing component. Generally, the general crossing polarizing power ratio XPR in the multi-path condition in the mobile communication is from 4 to 9 dB.
The PAG will be further described with assumption that the XPR is 9 dB.
FIGS. 21A to 21C are prior art illustrations showing using conditions of a portable wireless communication apparatus. FIG. 21A shows a portable wireless communication apparatus being used. FIG. 21B shows an enlarged side view of the portion A in FIG. 21. FIG. 21C shows an enlarged front view of the portion A. As shown in FIGS. 21A to 21C, the portable wireless communication is used at the position that the longitudinal direction is inclined by 60xc2x0. The PAG in this talking position provides the actual estimation index.
The prior art microstrip antenna apparatus and the monopole antenna apparatus cannot emit combined polarizing waves, that is, the polarizing direction is single. Thus, if the portable wireless communication apparatus is used with inclination, the main polarizing direction is also inclined, so that the actual PAG was insufficient. Moreover, the feed point impedance was high, so that the prior art antenna apparatus required a matching circuit to obtain the general input impedance of 50 xcexa9.
Moreover, in the prior art planer inverted-F antenna apparatus, an antenna current was distributed on the ground plane of the portable wireless communication apparatus, so that if the portable wireless communication apparatus is held by the hand or if it is placed on a metal table or the like, the radiation characteristic largely decreased. Thus, the actual PAG during communication was low.
The aim of the present invention is to provide a superior antenna apparatus and a superior portable wireless communication apparatus.
According to the present invention, a first aspect of the present invention provides an antenna apparatus comprising: a microstrip antenna above a ground plane, having a size corresponding to an operation frequency of said antenna apparatus; and a monopole element having a length corresponding to said operation frequency, one end of said monopole element being electrically connected to a point of said planer microstrip antenna, said microstrip antenna having a feed point at a predetermined distance from said point.
A second aspect of the present invention provides an antenna apparatus based on the first aspect, wherein said microstrip antenna comprises an inverted-F antenna including a short conductor for grounding at a distance from said feed point on the opposite side of said point.
A third aspect of the present invention provides an antenna apparatus based on the first aspect, wherein said microstrip antenna comprises a planer inverted-F antenna including a short conductor for grounding at a distance from said feed point on the opposite side of said point.
A fourth aspect of the present invention provides an antenna apparatus based on the first aspect, wherein said size is a half wavelength.
A fifth aspect of the present invention provides an antenna apparatus based on the first aspect, wherein said monopole element comprises a monopole antenna.
A sixth aspect of the present invention based on the fifth aspect provides an antenna apparatus further comprising: slidingly supporting means for slidingly supporting said monopole antenna; switch means; and a housing having a through hole and containing said inverted-F antenna, said monopole antenna, and said switch means and slidingly supporting means, wherein said switch electrically connects said one end to said point when said monopole antenna is extended from said housing through said through hole with said slidingly supporting means and electrically disconnecting said one end from said point when said monopole antenna is substantially contained in said housing with said slidingly supporting means.
A seventh aspect of the present invention based on said fifth aspect provides an antenna apparatus further comprising: slidingly supporting means for slidingly supporting said monopole antenna; switch means; and a housing having a through hole and containing said inverted-F antenna, said monopole antenna, and said switch means and slidingly supporting means, wherein said switch electrically connects said one end to said point when said monopole antenna is extended from said housing through said through hole with said slidingly supporting means and electrically connecting the other end of said monopole antenna when said monopole antenna is substantially contained in said housing with said slidingly supporting means.
An eighth aspect of the present invention based on said fifth aspect provides an antenna apparatus further comprising: switch means for electrically connecting and disconnecting said one end to and from said point to provide diversity operation between said inverted-F antenna and a complex antenna including said inverted-F antenna and the monopole antenna in response to a switch control signal.
A ninth aspect of the present invention based on said eighth aspect provides an antenna apparatus further comprising: communication condition detection means for detecting a communication condition using said antenna apparatus for generating said switch control signal in accordance with said communication condition.
A tenth aspect of the present invention based on said fifth aspect provides an antenna apparatus further comprising: a printed circuit board having a printed pattern for coupling said point to said one end.
An eleventh aspect of the present invention based on said fifth aspect provides an antenna apparatus, wherein said ground plane has substantially a right angle corner, said monopole antenna having a first portion which is in parallel to a first edge of said right angle corner and a second portion which is in parallel to a second edge of said right angle corner.
A twelfth aspect of the present invention based on said fifth aspect provides an antenna apparatus further comprising: a printed circuit board, wherein said monopole antenna is formed on said printed circuit board.
A thirteenth aspect of the present invention provides an antenna apparatus on said first aspect, wherein said monopole element comprises a helical antenna.
A fourteenth aspect of the present invention provides an antenna apparatus based on the first aspect, wherein a position of said feed point is determined by a distance from a zero voltage point at the microstrip antenna.
A fifteenth aspect of the present invention provides a portable wireless communication apparatus according to the above-mentioned aspects.